Hydrodynamic transducer

ABSTRACT

A motor pump impels a substantial volume of water through a rotatable, slotted shutter to modulate the flow of impelled water. A pair of oppositely facing, radiating-piston surfaces is reciprocably displaced in response to the modulated flow to project acoustic energy through a water media. The transducer, by being freely flooded, in independent of changing pressures in the surrounding media and does not require elaborate sealing assemblies, making it ideal for operation at extreme depths. Varying the configuration of the shutter, interconnecting conduits, and varying the angular speed of the shutter afford selective broadband operation, and increasing the flow rate provides a greatly increased power output.

United States Patent Rosenberg 51 Nov. 28, 1972 [54] HYDRODYNANIIC TRANSDUCER [72] Inventor: Edgar N. Rosenberg, San Diego,

Calif.

[22] Filed: Aug. 27, 1970 [21] Appl. No.: 67,460

Williams ..340/8 R Bricout ..181/.5 H

Primary ExaminerBenjamin A. Borchelt Assistant Examiner-S. C. Buczinski Att0meyRichard S. Sciascia, Ervin F. Johnston and Thomas G. Keough [57] ABSTRACT A motor pump impels a substantial volume of water through a rotatable, slotted shutter to modulate the flow of impelled water. A pair of oppositely facing, radiating-piston surfaces is reciprocably displaced in response to the modulated flow to project acoustic energy through a water media. The transducer, by being freely flooded, in independent of changing pressures in the surrounding media and does not require elaborate sealing assemblies, making it ideal for operation at extreme depths. Varying the configuration of the shutter, interconnecting conduits, and varying the angular speed of the shutter afford selective broadband operation, and increasing the flow rate provides a greatly increased power output.

2 Claims, 3 Drawing Figures PATENTEDNUV 28 I972 3 7 04 3 FIG. 3

INVENTOR. EDGAR N. ROSENBERG THOMAS G. KEOUGH ERVIN F. JOHNSTON ATTORNEYS HYDRODYNAMIC TRANSDUCER STATEMENT OF GOVERNMENT INTEREST The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

Background of the Invention Contemporary transducers having piston-like radiating surfaces enclosing ceramic stacks, or magnetostrictive prime movers, require elaborate sealing assemblies greatly increasing their complexity and cost. Such transducers are prone to failure after extended periods of high power operation and, when taken to extreme depths, are crushed if elaborate sealing assemblies are not provided. In addition, their operating characteristics, e.g., bandwidth, resonating frequencies, sensitivity, etc. are changed when their ambient pressures are varied.

Summary of the Invention The present invention is directed to providing a transducer of acoustic energy insensitive to pressure changes in a fluid media and includes a motor pump unit disposed in, and impelling, a variable quantity of the fluid media through a rotatable, slotted shutter arrangement to modulate the water flow. A pair of oppositely facing, acoustic energy radiating piston surfaces is in fluid communication with the modulated flow to effect a responsive, acoustic energy transfer through the surrounding fluid media.

The prime object of the invention is to provide a transducer independent of ambient pressure.

Another object is to provide a transducer not requiring elaborate sealing assemblies.

Still another object is to provide a transducer having a practically limitless power output.

Yet a other object is to provide a transducer of marked simplicity and resulting high reliability.

A further object is to provide a transducer having a motor-driven, rotatable shutter arrangement in fluid communication with a pair of projection pistons for effecting an acoustic energy transfer.

These and other objects of the invention will become more readily apparent from the following description when taken with the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. [is a side view of the invention.

FIG. 2 is a top view of the rotatable, slotted shutter disk taken along lines 2-2 in FIG. 1.

FIG. 3 is a side view, partially in section, of the acoustic energy projector taken along lines 3-3 in FIG. 1.

Description of the Preferred Embodiments Referring now to the drawings, the overall simplicity of the invention focuses attention on one of the marked advantages of.the invention, that being, its high reliability owing to noncomplexity. A conventional motor pump unit includes a sealed, oil-filled AC or DC motor 11 having its drive shaft journaled in a centrifugal water pump 12. As the pump is driven by the motor, ambient water is pulled in through an intake port 12a,

is centrifugally displaced within the pump, and is expelled through an outlet duct 12b to an essentially, cylindrically-shaped housing 13 via a first housing fitting 13a.

The housing serves as a support for a pair of op positely facing piston surfaces 14 and 15, each being carried on a separate, ring-shaped bellows 14a and 15a. The bellows are elastomer rings or metallic rims having a corrugated cross-sectional configuration and possessing the capability for withstanding repeated violent reciprocations.

A few small holes 14a and 15a are optionally, randomly provided in the bellows to allow air, which is otherwise trapped, to escape from the housings interior. For an optimum energy transfer, the transducer preferably is flooded completely to fill the housing to ensure a more efficient acoustical coupling of the inside of the piston surfaces to impelled water.

A plurality of rods 16, each mounting a powerful, helically shaped biasing spring 16a on opposite ends, reaches through both piston surfaces and across the cavity defined in the cylindrical housing to limit the outward travel of the piston surfaces as they are oppositely, bidirectionally displaced and to return them to a center or normal position. The waters pressure, as it is pumped by the motor pump unit and the forceful impulses of the modulating on-off" sequence, to be explained below, would tend to permanently deform the bellows or tear them from the cylindrical housing, were it not for the powerful biasing springs.

Impelled water from motor pump unit continues on its course and passes through and from the cylindrically-shaped housing via a second housing fitting 13b and finally reaches a flow-modulator assembly 20 carried on the housing.

In a preferred form, the flow-modulator assembly is a brass, conical casting, open at its end where joined to the second housing fitting, and closed at its upper, opposite end by a plate 21 shaped with a plurality of radially-extending apertures 21a. At its center, the plate coaxially mounts a heavy duty pin 22 rotatably carrying a slotted shutter disk 23. Slots 23a are machined in the disk having, optionally, the same dimensions as apertures 21a and spaced to ensure an alternating alignment-and-covering coaction between the slots and apertures as the disk rotates on the pin. The alternate alignment-and-covering modulate the impelled flow of water to produce an on-off switching sequence. This sequence creates a succession of impulses that are hydraulically transferred to piston surfaces 14 and 15 causing their responsive, reciprocal displacement.

The rotatable slotted shutter has a circumferentially carried gear 26 engaged by a correspondingly shaped driving gear 25 mounted on the shaft of a variable speed motor 24. By selective control of the variable speed motor the rate of angular rotation of the slotted shutter is changed and a variable frequency modulation capability is provided.

What has been described is the invention in its most basic form. Its operation calls for the transducers being disposed in the transmitting media and the waters filling the transducers innards.

A source of electrical power for driving motor pump unit 10 is connected and a modulating source is coupled to motor 24. Water, drawn in through coaxially located intake port 12a and expelled through outlet port 12b, is fed through the acoustic energy projector, cylindrically-shaped housing 13 and in contact with the radiating piston surfaces.

As the impelled volume of water passes through second housing fitting 13b and into flow-modulator assembly 20, it is forced through the aligned slots and apertures as slotted plate 21 is rotated.

The high volume of water passing through the transducer (in one operational embodiment, over 1,800 gallons of water per minute were pumped) causes an onoff switching sequence creating a high energy transfer of acoustic energy from reciprocating, radiating piston surfaces 14 and 15. The power output is determined by the pumping rate; the frequency of operation and wave shape of the projected energy primarily are a function of motor 24 speed and slot-aperture configuration.

Modifications, providing more flexibility in frequency response, bandwidth, etc. are feasible and call for matching the transducers mechanical impedance to the water media with different structural lengths, diameters, and internal configurations of the aforedescribed members. A specially designed tuned sleeve 20a carried on the downstream side of the flow modulator enhances impedance matching and optionally is included.

Obviously, many modifications and variations of the present invention are possible in the light of the above teachings, and, it is therefore understood that within the scope of the disclosed inventive concept, the invention may be practiced otherwise than as specifically described.

What is claimed is:

1. A transducer of acoustic energy insensitive to hydrostatic pressure changes comprising:

an electrical motor-centrifugal pump unit for drawing in water from the surroundings and for impelling the flow of water;

means hydrodynarnically channeling said flow of water from said motor-centrifugal pump unit; modulating unit shaped to define a cone-shaped chamber being connected at one end to the channeling means to receive said flow of water and having at its opposite end an apertured end plate for passing said flow of water therethrough to said surroundings, a shutter disk joumaled onto said apertured end plate provided with slots similarly dimensioned to said apertures, and a variable speed motor mechanically engaged to said apertured end plate and by selective rotation of said .apertured end plate by said variable speed motor said flow of water is modulated as an off-on sequence; and cylindrically-shaped housing interposed between said channeling means and said modulating unit to receive and to be filled with said flow of water therein and having a pair of oppositely facing piston surfaces each carried on an annular bellows in direct contact with the modulated said flow of water for projecting said acoustic energy by responsive reciprocal excursions thereof.

2. A transducer according to claim 1 in which a plurality of holes are provided in each said annular bellows to allow air to escape to ensure the filling of said housin and a luralit of rods each mountin biasin sp ings exteiids thr ough both said pair of pl ston sur faces for recovering same to a neutral position after said responsive reciprocal excursions. 

1. A transducer of acoustic energy insensitive to hydrostatic pressure changes comprising: an electrical motor-centrifugal pump unit for drawing in water from the surroundings and for impelling the flow of water; means hydrodynamically channeling said flow of water from said motor-centrifugal pump unit; a modulating unit shaped to define a cone-shaped chamber being connected at one end to the channeling means to receive said flow of water and having at its opposite end an apertured end plate for passing said flow of water therethrough to said surroundings, a shutter disk journaled onto said apertured end plate provided with slots similarly dimensioned to said apertures, and a variable speed motor mechanically engaged to said apertured end plate and by selective rotation of said apertured end plate by said variable speed motor said flow of water is modulated as an off-on sequence; and a cylindrically-shaped housing interposed between said channeling means and said modulating unit to receive and to be filled with said flow of water therein and having a pair of oppositely facing piston surfaces each carried on an annular bellows in direct contact with the modulated said flow of water for projecting said acoustic energy by responsive reciprocal excursions thereof.
 2. A transducer according to claim 1 in which a plurality of holes are provided in each said annular bellows to allow air to escape to ensure the filling of said housing and a plurality of rods each mounting biasing springs extends through both said pair of piston surfaces for recovering same to a neutral position after said responsive reciprocal excursions. 